Improvement in iron bridges



` 6 Sh'eets--She-et 1; D. HAMMOND, M. ADLER 81.1. ABBOTT. Irun-Bridges.` N0.135,802.

Patented Feb. 11,1873.

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' Patented Feb. 11,1873.

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AM. PHarH/momP/f/c ca N1( ossofms's pfeacfss) i UNITED lSTATES PATENT OEEIO DAvID HAMMOND, MICHAEL A-DLEB, AND JOB ABBOTT, OE CANTON, OHIO.

INIPROVEMENT IN IRON BMRIDGES.

Specification forming part of Letters Patent No. 135,802, dated February 11, 1873.

.To all lwhom it may concern: A

Beit known that we, DAVID HAMMOND, MICHAEL ADLER, and JOB ABBOTT, of Canton, in the county of Stark and State of Ohio, have invented certain new and usefl Improvements in Arch-Girder Bridges; and that the following is a full, clear, and exact specication thereof, which will enable others skilled in the art to make and use the said invention.

It is well known to bridge constructors that the principal defect in the practical working of bow-strin g girders as heretofore constructed, especially in long-spans, has beentheir want of suficient stiffness toresist the action of a rolling load; that the lack of vertical stiffness hasusually resulted from the want'of suftcientcompressive capacity in the posts, and the lack of lateral stiffness--rst, from want of proper rigidity in the lower brace-beams; second, from the imperfect manner of securing points of the arch by struts from the bracebeams 5 third, from the insufficient character ofthe overhead lateral bracing between the bridge-girders; and, lastly, from the-want of sufcient lateral capacity in the arches of the girders; and that great difficulty has been experienced in overcoming these objections to this class of highway bridges, especially in this country-first, because the requirement ofcheapness has prevented the use of exact i and expensive details of construction in said shop; and, lastly, because therequirement of'` sidewalks for highway bridges, in many cases, limits the width of the lbearing `between theA lower beams andarches, so as to make it very' difticult to obtain the proper lateral strengthl in lon gspans, where the distance between the arches and chords is very considerable.

Our invention is designed to obviate'these obj ections to the plan of bow-strin g-girder construction for. bridges of moderatev spans, and

to make it applicable to long bridge-spans, in

which it has heretofore been considered inapplicable; and to this end it-consists in the combination, with a bow-string girder,`of an iron lattice girder-brace post, which has an adjustable attachment either at the chord or arch of the girder, or at both of said points, and which is solidly secured to the lower brace-beams of the bridge and to the arch, so as to oppose the transverse stiffness of the lattice-girder to a any tendency of the arch to move in a lateral direction. Said invention also consists in the combination, with the arches of the bridgegirders, of an iron lattice overhead girder, which is raised above the arches in order to give the proper headway on' the bridge in cases where it could not otherwise be used, or which is used between the arches in cases where there is sufficient height to give the proper headway, and which, in either case, is rigidly secured to the arches, so as to oppose the transverse stiffness of the lattice-girder to an y tendency to a lateral motion of the arches and girders. Said invention also consists in the combination, with the arches and brace-posts, ofthe bow-string girders of abridge, oi an iron lattice overhead girder, which is rigidly secured to said arches and to the lattice-posts below the arches, so as to oppose the lateral motion of the arches by both the transverse stift'- ness of a lattice-girder of considerable depth and by the strength ofthe brace-post against a force applied to bend it at a point considerably below its head, and hence acting with less leverage than it' appliedto the arch, as in the case of the overhead lattice-girder described in the preceding clause. Said invention also consists in the combination, with the lattice brace -posts and overhead lattice girders of a 4bowstring girder bridge, of atension-rod extending `from the outer part of the lower brace-beam across `the post to the overhead lattice-girder, and acting as a tensional tie, in combination with the brace-post acting asa compressive strut .insecurin g thearches and girders against lateral motion. VSaid invention also consists in the combination, with the arches of a bonstringgirder bridge, and with the lateral overheadmembers at the heads of the brace-posts,

of lateral overhead struts secured to the arches 4at the heads of the intermediate posts betwee the brace-posts, and connected by half-rings at their centers to the lateral diagonal tiesv from the ends of the lateral members at thev heads of the brace-posts, by which means thc archesare secured against lateralbending at the heads of the intermediate 'posts without any addition ot' diagonal ties above those re` quired to brace the arches only at the heads of the brace-posts. Said invention also consists in the construction of an arch composedv of a central horizontal plate' and two segments ot the Phoenix or Keystone column on each side as the essential base of construction of the arch, and having combined therewith'suit able plates, channel-bars, and columnlsegments, as is hereinafter lnore fully shown, the

whole forming a double tubular archin which therequiredcompressivecapacityibrlongspans is obtained invconnection with such breadth of arch as to prevent any danger of lateral deection. Said invention also consists in the combination, with the lower chords and brace posts of a boW-string-girder bridge, of a pair of rolled channel or I beams, trussed by a hog-chain on the under side, and held from upward deection by a tension-:rod on the upper side, said pair of beams extending from girder to girder of the bridge, and forming supports for the oor-joists ofthe bridge, as well as brace-beams for the system of bracing for the bridge. Said invention also consistsin the .novel details of construction for the lateral hitch-blocks for theat-tachment'of the lateral diagonal ties to the brace-beams orvlateralY girders, the girder-blocks ,for the attachment' oi'vthelateral overhead girders to the braceposts, the arch-blockvfor theattachment of the lateral overhead struts to the arch at the' heads of the intermediate posts, the combined wrought and cast iron Ychord-plate for' the attachment `of the vertical diagonal ties, and the connect-ions fory the brace-beams and posts, these several improvements in detail making our b'efore-.specihed improvements in bracings ot easy application to the otherparts of the bridge,'and greatlyfacilitatin g the constructiony of the bridge in the shop and its erection on the bridge-site. Y In the accompanying drawing, Figurenl is an elevation of a half-span'uoi'abow-stringgirderbridge illustrating ourimprovements i Fig. 2 isa plan of the same,'showing a halt'- plan of the arch and bracing and ahaflt'plan of chords.` Figs. 3, 4, and 5 are side views of posts Nos.-2, 4, and 6 of said *girden f Fig. 6"

is a `central crosssection otlnidge atv post No. S, showing the deep overhead lattice-girder and two modilicationsiof lthe lattice brace'- poists. Figs. 7 are enlarged v.detail viewsot' the end of the raised overhead.lattice-girder audits arch attachments. (Figs.` S are' viewsot' ani'noditied formof the' saine. Figs. 9 are detailvieufs I of the connections for theoverheail'lattice-j A girderbctween the arches. Figs. 10 arebfvletail views of theconnections for the overhead lat;

ticegirders between thearches'and bra ce-posts.

Figs. 11 are detail views ofthe half-ringconnections at the centers ofthe lateral overhead struts'. Figs. 12 and 13 are detail views of mod# ied forms ofthe constructions shown in Figs.

10. Figs. 14 are detail views of the arch-con-l nections for the lateral overhead struts. Figs.

15,16, and 17 are'detail views of thelower chord-connections for posts Nos. 2, 1, and 3. Figs. 1S, 19, 20, and 21 are detail viewsof the lower chord-connections for posts Nos. 7, 4, 6, and S. Figs. 22 and 23 are detail views of the ca-st thimbles for the brace-beams. Figs24 are elevation and plan of portion of bow-string girder, showing one form of our improved arch and brace-beam construction. Fig. 25-is an enlarged end view of the same. Fig. 26 isan end view of the brace-beams in Fig. 25. Figs. f 27 are detail lviews of the brace-beam and post-blocks. Figs. 28 and '29 are elevation,` plan, land enlarged end view of a modified form of our'improved arch and brace-beams.

A is an arch of the general form described in Letters Patent No.'l02,392, granted to D."

Hammond and J. Abbott April 26, 1870. The ends of said arch abut against cast shoes B,

which rest on the abutments, and are con-l nected by the chords C, composed of two or more plates of iron placed edgewise and abreast, and upon which the Wooden oorjoists for the bridge are usually placed. The struts or posts VNos.`1 to 8 and the diagonal ties Al are arranged between the chords C and arch A, and ironbrace-beams T are placed on I the chords, usually at the foot'of everyother post, as in the ordinary plans of bow-string-l girder construction, said brace-beamsbeing united by diagonal ties U placed below 'the' bridgelflooring, so 'as to form, with the chords. C and ties U, a rigid ysystem ot' lateral bracing,

by which any lateral deflection of the bridge at'the chord-level is prevented; the principal features 'of our vinvention consisting, rst, in

the improved construction' of the brace-posts 2,4, 6, and 8, by which the arch A is secured laterally from the system of bracing between the chords C; second, in the improved construction' of the vlateral overhead bracing,

where the span of the bridge is such las to allow ofthe use of said overhead bracing; and, 1 lastly, in the improved construction of ther arches A, by which the lateral capacity ofthe arches themselves is so increased as to adapt them to very long spans.

We will describe the details of our improve-z ments in the order indicated, that the mechanic may understand the application of our improvements to such length of spans as :he f

may vhave tol construct.

The 'triangular' lattice-posts 2, 4, and 6 are.Y specially designed for bridges without sidewalks,in which the projection ot' the post beyond the outer plane 'ot' the 'arch 'offers no vobstruction to travel; and it is usually constructed of 'four an gie-irons,'ff, placed two at each side,' and having between them the latticc-`barsF,.

which are securedby rivets run 'throughthe parallel ilanges ofthe angle-bars and the ends of the lattice-bars, and through the crossings of the lattice-bars. The flan ges of theauglebars at right angles to the plane of the posts are herey shown on the inside, or toward the center of the posts; but, if preferred, theycan be turned to the outside ofthe posts, and plates can be riveted to them to increase the capacity of the posts; or T-bars or star-iron (sometimes called X-iron) can be used at each side in place oftwo angle-bars, the lattice-bars being riveted yto one leg of the 'I' or X bar. The upper ends of the angle-bars f are riveted in the recessed faces'of the attened ends j" of the arch-bolt F', (see Figs. 7 9, and 14,) which passes through'the arch A, and is secured by jam-nuts above' and below the arch; and in theform of chord-connection shown in Figs. 15 theinner angle-bars f..` are bent out at a, to pass down on each side of the brace-beam T, andare iiattened and headed below' to iit between andsupport the chord-'bars4 U C, which are clamped .to them by through-bolts4 C' C'. The lower ends of the outer angle-barsf have riveted between them the bolt b, which extends down through a cast thimble, c, with jam-nuts above and below, the rear end y of said thimble (see Figs. 22) being of the form l of the cross-section of the brace-beam T, to

the end of which it is secured by a strap, c'j, which iits around the recessed partof the thimble-body, and to the web of the brace;-

lbeam, to which it is riveted or bolted; the

below. The form of chordfconnection shown in Figs. 19 is, however, preferable to that shown in Figs. 15, as `it avoids-any blacksmith-work on the angle-barsj. It consists of a bolt, E, having Fa broadriiat head, e, which fits over the beam T, and is riveted to the bars/,and which passed down between the lchords C through Va washer, Y', which is grooved to admit the'chords, so as to hold them in position, and beneath which may be placed the tiefplate D, through which the boltE extends, with nut below, as shown. The tie-plate D is designed to obviate the necessity of punching thechords C for a bolt to pass through the eyes on the lower ends of the diagonal ties A', which are placed between and secured toy said chords in this way inthe three end panels ofthe girder, shown in Fig. 1, and it consists of a wrought-iron plate having its end cut out in the center and'turncdover to form eyes d, like those on the broad -leat' of a strap-l1inge the ties A' being secured to said plate by pins d' passingthrough: said eyes d d, and through thiscase extend down between the chordsC' andbetween the eyesd d, as shown in Figs. 1 9. Figs-.20 shows a modified form o f thev chordconnection in Figs. 19.two bolts, E'E, being of the single bolt` E inthe former case; the beam T being held from sliding, in this as in the former case, by clamping it between the chords C and bolt-heads e, or the ends of the angle-bars f, thus obviating the use of the bolt t, shown in Figs. 15. The intermediate posts 1, 3, 5, and 7 are designed to act simpl y as ties or struts without aiding materially in securing thelateral stability of the arch, and are y constructed of four an gle-bars, ff f j', riveted back to back in column form, with intervening thimbles, in the form shown in detached section 8' in Figs. 13. Their upper end s have an arch-bolt, F', lriveted into them, in the manner described in Figs.'7, by which they are attached to the arch A, and the chord-connec tions are made either by a headed plate, E", riveted between their lower ends and secured betweenthe chords GAC by bolt C', as shown in Figs. 16, or by means ot'two bolts, E', riveted between the angle-bars, and run down between the chords G, and through a grooved washer,Y', as shown in Figs. 17 5 or,where an adjustment in length at the lower end of post is desired, the single bolt E' may be used, with a grooved washer, Y', above and below the chords O, and with jam-nuts above and below said chords, as shown in Figs. 18.

The tie-piece Y shown in Figs. 18 is designed to be used in place of the tie-plate D in Figs.

19, andconsists ot' a short piece of plate-iron with flanges bent on each edge, or oi rolled channel-bar, or ot'rolled beam, havin g a space,

y, cut out of its web at each end, and havingN its heads punched for the passage of the tiepins d. made to fit in the upper part of the piece Y, and a filling-piece may be used on its under side to form a bearing for the nut on the lower end of the bolt E'.

The form of post shown at 8, Fig. 1, and in Figs. 6, 10, 12, 13, and 2l, is5r designed particularly for bridges with sidewalks, in which the width ofthe post should not exceed the width of the arch. The angle-bars ff composing its sides are placed parallel, instead ot' at anan- A gle with each other, and are riveted to the lat` the angle-bars more effectively against bucle ling in their bent parts. the eyes on'the ends'of the ties A', which in.

Where the sidewalklpost is used in connection witha deep overhead girder, as shown on right Vhand in Fig. 6 and in Figs. 13, the angle bars f can'be brought togethernear the lower edge ofthe overhead girder, and fror'nthence runupgto the arch-boltF'in acolumnform, as

The lower grooved chord-plate Y' is shown, their upper portions being united, in

the formshown in detached section 8'-, by means ot' rivets and intervening thimbles.

If no adjustment of the arch-and-post connection is required, the plate L may be riveted between the angle-,bars f, as shown in Figs. 12, and the arch-bolt F' be riveted to said plate, as shown, the ends of the angle-bars simply abutting against the arch-flan ges, or being bent over and riveted to said iianges, as shown.

The .bolts E are riveted between the lower ends of the angle-bars f, as shown in Figs. 21, and are secured in cast thimbles c, which are made with a rear ange, 13, shown in Figs. 23,V which fits into the brace-beam T, to which said thimbles are secured by straps 14 bent into and around the recessed body of the thimble, andlying up to the web ofthe beam, to which-they are riveted. This connection secures the post tirmly `to the brace-beam instead of to the chords, as in the other forms of posts, and the beam is secured to the chords C by bolts 15,

which run through thimbles c (secured `onv each side of the beam T in the mannerv just shown) and pass down between the chords C, below which they are'secured by washers and nuts in a manner evident from the preceding descriptions.

Where the span of the bridge is from ninety to one hundred feet and over it becomes practicable to use overhead bracing for vthe arch, the first form of whichthe raised lattice-girder shown in Figs. 4, 7, and S-is used where the distance between the iioorin g ot' the bridge and arch is insufficient to allow ot' the placing of the girderbetween the arches. This girder is usually constructed of four angle-bars, g, although T or X iron can be used, as inthe brace-posts, with in-` ter-veninglattice-bars G riveted at each cross-` ing; and the end angle-bars g are combined with the body of the -girder by plates L K riveted in at the corners of the girder, as shown, by which a very rigid construction is etl'ected; though, itl preferred, the lattice-work G can be carried out in place ot' the plate L, and the plate K be omitted; or either of the plates L or K may be used and the other omitted; but the use ot' both plates isto be preferred. The end angle-bars g g rest on the archlian ges, to which they may be riveted by bending out their ends, and the bolt H is riveted to the plate L and runs down through the arch, with nut below, as shown in Figs. 7. In the moditied and cheaper,.though less rigid, form ot' construction, shown in Figs. 8, the arch-bolt ll is iiattened out and riveted between the anglebars g g, the end angle -bars g and .plates L K being dispensed with.

At those points where the distance between the. lioorng and arch is sufficient to admit ot' it, the lattice-girder, shown in Figs. 5 and 9, is used, the depth ofV the girder. being the same as that of the arch, and its ends -iitting up to the arch, to which it is secured by plates O O riveted to the upper and lower` an gle-bars g, and having'holes for thepassage'of the arch-bolt F at the headof the brace-post.

At those points where the distance between the bridge-liooring and the'archis considerably more-than the headway requiredthe deep lattice-girder,'shown in Figs. 6,10,12, and 13, is used, the object l'beingto secure greater transverse stiffness than could be economically obtained in the shallow' girders, shown in Figs.- 4 and 5. These deep girders are constructed with vangle-bars gig g and llattice-bars G, in the same manner as the shallow girders before described, the bars' G', of angle or T iron, being riveted at intervals on the lattice-bars, as shown in Fig. 6, to stiften the lattice-work against buckling sidewise. The upper corners of the girders are secured to ythe archesA by plates O riveted. to the vupper angle-bars g, which rest on the arch A, and through which the arch-bolts F arepassed. The lower corners of the girders are` secured to the brace-.posts by bolts 16, which pass between the angle-bars f of the posts 7 through a washer at their back, and through a girderblock, G which is riveted to the lower anglebars g ot' the overheadfgirders, as shown in Figs. 10 and 13, the bolt 16 beingheld by jamnuts from sliding in either the girder-blocks G, or between the augle-barsf, when the neck brace-posts, shown in Figs. 13, are used. The use of the girder-blocks Gfallows ofthe placing of the deep girder in position between the arches and posts after the bridge-girders have been raised, the bolt 16 being inserted after the girderis placed in such position, which is a great convenience in putting up the bridge, and which could not be conveniently-effected were the bolt 16 riveted to the girder-Han ges.

Where the straightsided post, shown in Figs. 12, is used, the girder is attached to the arch by a T-shaped plate, O', riveted tothe girder and arch. anges, as shown, and by one or more clamping-bolts, 17, run between the angle-bars of the lattice posts and girders, and beariu g on washersA at each end.

As will be seen in Fig. 2, the overhead lattice-girders G, of some of the forms just described, are used at the heads of each of the brace-posts 4, 6, and 8, where the height of the arch admits of their use. But-these are alternate posts in the girder; and in order to brace the arch at the heads of the other posts 5 and 7, the lateral struts()J are used, these struts usually'consistin'g of four angle-bars, q q, riveted together in column form, although other forms of compression members may be used. The-bolts Q are riveted to the endsot' `these angle-bars, as shown in Figs. 14, and

`to by the bolt F', and one or more additional bolts when required. f The `half-rings It are rivetedbetween'the an gle-bars q q of the struts Q, as shown in Figs. 1l, and on the tops ofthe v lattice-girders Gare riveted the hitch-blocksN,

which are secured by rivets passing down through the body of the blocks and the flanges of the girders, and which have holes for the passage of the lateral ties, and beveled end faces for the nuts at the ends ot the lateral ties, and said ties P are run from the hitchblocks N on the first girderG to the half-rin g Ron the rst strutQ; thence from the oppo` site half-ring'R on the same strut to the hitchblocksfN on the next girder G, and so on, as shownin Fig. 2, thus .forming a system of brace-'ties between` the girders Gr, and at the same time securing the struts Q, and consequently the points ofthe arches at their ends,.

against lateral motion. The action of the lateral ties P on the first or raised lattice-girdery G tends to bend said girder oversidewise, to :prevent which a tie-rod, M, (see -Figs.1 and 7,) -is run from near the top ofV said girder toa point, on the arch considerably back of the girder; or, if preferred, a strut, M', can be used between the ginder and arch, as indicated by` y dotted lines in Figs. 7. To aid the brace-posts 8 in resisting lateral deflection the tension-rods 1S are run from thimbles c at or near the ends of the brace-beams T, across the posts 8, to the lower angle-bars of the overhead girders G,,to which they are attached, as shown in Fig. 6.

v The construction and application of the lattice-posts and overhead girders to the bridge-` girders being thus fully shown, their action in; preventing any lateral -deiiection of the bridge,

arches, or girders will be evident `from an inspection oi' Figs. 4 to 6, in 4which the4 arrows L represent forces tending to deflect the arches and girders laterally, and the arrows R the resulting direction of strains thrown on the differentparts of `the bracing, from which it w-ill be evident that nolateral ymotion of either the arches or girders can possibly take place without overcoming 'the transverse strength of one orv more of the lattice members of the bracing,-which` are of.such form that, `with a very moderate amount of metal,

\ they can be made suiiiciently strong to bear.

with the well-known `column and channel-iron.

arch, as being `the form of arch to-which these' plans of lattice brace-post-and-girder construction have been the most extensively applied,

and we will now describe our improved form of arch and brace-beam construction, by means "of 'which the planof bow-string-girder con-1 struction can be" appliedjV to almost any re-y quired length of span: The essential features of our improved arch consist of the horizontal plate h, which may be made of any widthrequired to obtain the proper lateral capacity for the arch, and to which are riveted the four column-segments m n m u, two at each side, as shown. With these five essential parts are combined such other segments, channel-bars, and plates as may be required to forma double tubular arch of the proper cross-section-as, for example, in Fig. 25, the four segments u u u u are riveted to the parts m n h, so as to form a double tubular arch with two tubes` of a circular section, and in Figs. 29 the channel-bars x .fr and plates w are riveted to the parts m fn, so as to form a double tubulararch of considerably greater capacity than that shown in Fig. 25. If a still `greater capacity were required, two columnsegments could be used in place of the plates `w in Figs. 29, so as to form two arch-tubes of the same section as the arch A, shown in Figs.

.9, as shown in detached section above Fig.

29, the plate h extending the full width of the arch, as shown, or only between the two tubes, a-s preferred; while, if a smaller section than that shown in Fig. 25 were desired, plates could be used in place ofthe column-segments shown in Fig. 25, thus forming a Adouble tubular arch of the form shown by detached section between Figs. 24 and 25, the particular form of arch to be used in any case depending on the bridge-span and load, and being, therefore, a matter ofjudgment for the constructor. The construction-of the lattice-postsfF in Figs. 25 and 29 and the mode of attaching them to the archesy are similar to those shown in Figs. 12 and 10, and need not befurther described here. i Where the span of the bridge is very longsay two hundred and fifty-feet and overthe width of the roadway vshould be twenty feet and over, in order .to secure proper lateral stiffness at the chord-level, which is the basis of all the bridge-bracing; but this Width of track makes the use of wooden tloor-joist, ex?

tending from chord to -chord of girders, objectionable, and makes the use of iron floor-girders at the foot of each post desirable; while, in

order to secure the. best-results invertical stiiiness in theV girders, the panels should be made' of .considerable len gthy-say from fifteen to eighteen feet; and this makes it desirable that eachk post should be a brace-post, and consequently thateach iron tloor-girder should act as a brace-beam. to accomplish which we make said girders of a pair of :l2-beams T T of moderate depth, Vwhich aretrussed below,

against: downward deflection by the-bridge-y load, by a heavy. hog-chain, t', attached to the beams next their ends by pins run through the webs of the beams,and running down under supports t" fi on-the underside of the beam, and which are heldagaiust upward deflection byA theoutward movement-ot` the arches by a tensiomrnd. i, having an adj ustableenter supf port, i,"onthe beams T'. j l f 'lhre'e plate-chords, C, are shown in Figs. 2t

and 25, in which. case the girders T' T' are se.

cured toy said chords by bolts 22 rundown between the chords,th r'ou gh the grooved washers Y'fabove and below.'tl1e chords, and the tieplate D forthe doublesetot diagonal ties A', down betweenV the beams T' T', beneath which they'are secured by washer and nuts.

The bolts E' are riveted to the angle-bars of the post F, and are secured by jam-nutsvin the hole 2l ot' t-he piece l, (see Figs.27,') which has the lugs 20 20 at its sides, and which iits in between the beams T', where it is secured by bolts k run through the webs of the beams and the lugs 20'.

In;1 `igs. 28 and 29 four chords, C, are used, which are arranged in pairs under the sides ot' the post F, in which case the bolts E', riveted to the angle-bars of said posts, run down between the two chords and the two beams, and through the grooved washers Y' and tie-plates D, as shown, and are secured b vwasher and nutsbelow the beams, thus dispensing with the use ot the bolts 22 and beam-pieces l in Figs. .4 and 25.

`Having thus fully described ourinvention,

vwhat we cla-im therein as new, and desire to secure by Letters Patent, is-

1. The combination of an iron lattice bracepost with the arch and Vbrace-beam ot' an iron bow-strin g bridge, said post having a vertical adjustment either at the arch or chord end. or at both ot' said points, substantially as and for the purpose speoitied.

2. The tilling-plate V, in combination with the. bent parts oi' the side bars ot' a lattice brace-post, F, t'or the purpose ot' preventing the buckling ot' said bent parts when the, post is subjected to a compressive strain, substantially as specified.

3. The archbolt F', having aiiattened head or bea\'ertail,j", with recessed faces to receive postbars f f, substantially as shown and specified.

4. The chord-bolt E with broad head e, in combination with the inside barsf of the lattice brace-post of a bow-strin g bridge, substantially as and for the purpose specitied.

5. The combination, with the arches of a bow-string bridge, of an iron lattice-girder, Fig. 5, placed between said arches, and rigidly secured thereto by plates o o attached to its corners, and secured above and below the arch by a bolt run through said plates and arc, substantially as and for the purpose spectie o'. The combination, with the end of araised lattice-girder for bow-string bridges, of an arch-bolt, H, rigidly secured to said girder, and extending down through the arches of said bridge, substantially as and for the purpose l, specited.

bridges, having its endbars g' g' arranged with bearings on the extreme-horizontal parts of the arch A, and with -a bolt, H', rigidly securing it' to said arch,.substantially as specified.

8. The combination, with the raised latticegirder, Figs..7, and arch-A, of a tie,,M, or strut M', forholding said girder against the action y of the lateral ties P, substantially as specified.

9. The combinatiomwith` thev arches and brace'posts of an iron bow-string bridge, ofthe deep iron lattice-girder, Figs..6 and 13, secured tothe arches at its upper corners by a plate, o or o', and at its lower corners to the posts at e points considerably below the arches by one or more bolts, 16 or 17, substantially as and for the purpose specified.

10. The girder-block G", secured on the lower corners of the deep lattice-girders specified in preceding clauses, substantially as and for the purpose specified. 11. The combination, with the brace-beam, post, and overhead lattice girders of a bowstring bridge, ot' a tension-rod, S, extending from the outer post ot' brace-beam across the post to the overhead lattice-girder, substantially as and for the purpose specified.v

12. The lateral hitch-blocksN for the attachment ot' the lateral ties to the brace-beams or overhead gir-ders, said blocks having holes arranged t'or the passage on both ties and beveled end t'aces for the nuts of said ties, and being secured to said beam or girder by bolts or rivets passing through the body ot' the block and the flanges ot' the beam or girder, substantially as specified.

l5. The. lateral compressive strut Q, secured to the arches ot' a bow-string bridge at the heads of the. intermediate posts, and connected at. its center by lateral ties to the ends of the lateral strut or girder at the head of the brace-posts, substantially as and for the purpose specified.

14. The arch-block W, rigidly secured to the arch A, and having an eye or hole, in which the end bolt of the lateral strut Q can be secured by jam-nuts, substantially as specified.

15. The grooved washer Y' and wroughtiron tie-plate D, in combination with the chords U and post-bolt E or clamping-bolt 22, substantially as and t'orthe purpose specified.

16. The tie-plate Y, consisting of a short piece of hanged iron plate or its equivalent, having its web cut away at y y, and with holes formed in its ilanges for the insertion of the tie-pins d', substantially as specified.

17. The cast end thinible c, having its end of the form of the section ot' the brace-beam T, and secured thereto by strap e', fitting into the recessed part of thimble-body, and to the web of the brace-beam, substantially as specitied.

y18. The cast side thimble c", having a rear liange, 13, Iitting between the iianges at the brace-beam T, and secured' thereto by strap 14,*V tti'ngffinto recessed part of thimble-body, substantially-as specified. i

19.#A Wroughtgirondouble tubular arch, havin'gs the base of construction ehorizom talplalte, with two column-segments let each side, said base' having combined with it suit-- able '-plates, channel-bars, and segments, to form n' arch ot'lthe required cross-section and lateral capacity, substantially as is herein specilied. j

2Q.4 The combina-tion, with the lower chords and brace-posts of a bow-string bridge, of a pair of rolled I or channel beams, trussed byV :t hog-chain on the under side, and held from .upward deflection by a tension-rod on the upper side, substantially as and for the purpose specified. Y

As evidence of the foregoing, witness om" hands this 25th day of September, A. D. 1872.

DAVID HAMMOND. MICHAEL ADLER. JOB ABBOTT.

Witnesses:

JENNIE M. GRANT, GEORGE E. BUCKLEY. 

